Therapeutic Efficacy of PRF-P and Oncolytic Adenovirus in Glioma.

Introduction: Oncolytic virotherapy is a potentially interesting approach for treatment of cancer, including glioblastoma. Recent studies in this area suggest a synergist approach for combining oncolytic virotherapy with immunomodulatory approaches. In this study, we have examined the role of platelet rich fibrin patch (PRF-P) to enhance anti-tumoral immune response when used in conjunction with tumor specific oncolytic Ad5RGD-CMV-E1Δ24. This PRF-P is derived from blood, enriched with lymphocytes, platelets, macrophages (M1) and pro-inflammatory cytokines. Application of PRF-P has been shown to enhance immune cell migration and proliferation. Hypothesis: We hypothesize that PRF-P provides local immunomodulation by supplying pro-inflammatory chemokines as well as recruiting and enhancing proliferation of cytotoxic T cells, which may lead to an enhanced anti-tumoral immune response when combined with oncolytic virotherapy. Methods: Blood from donor mice bearing GL 261-OVA and murine glioma cell line expressing ovalbumin (OVA) as a model antigen were collected into non-anticoagulant tubes and processed according to platelet-rich fibrin protocol. Five days after tumor implantation, a stereotactic intra-tumor injection of Ad5RGD-CMVΔ24 viral vector was performed. 48 hrs of post viral vector administration, a craniotomy was performed and the autologous PRF-P was applied over the tumor. For the immunological flow analysis and immunohistochemical analysis, mice were sacrificed five days post treatment to harvest the organs. Results: We first performed a survival analysis in immuno-competent murine model. Mice injected with oncolytic virus alone had a significantly prolonged survival compared to PBS treated group (P<0.001). In addition, when used in combination with immunomodulatory PRF-P, this prolonged survival benefit was extended (P<0.001). Also, immunohistochemical analysis showed that a decreased size of implanted tumor in both virus alone and combinatory treated groups. Most interestingly, we observed a increased number of tumor specific CD8+ cells and antigen cross-presenting and lymph node tropic dendritic cells (CD11b-/CD11C+/ CD103+) from therapeutic treatment groups. Conclusion: Our observation collectively represents a novel anti-glioma oncotherapy and immunomodulatory approach and provides a platform for the evaluation and translation of this promising anti-glioma strategy. We will further discuss additional immunomodulatory application: oncolytic virus expressing checkpoint inhibitor, PD-1 along with the PRF-P treatment.